The production of linear alternating polymers of carbon monoxide and at least one ethylenically unsaturated hydrocarbon has been known for some years. Nozaki, U.S. Pat. No. 3,694,412, produced such polymers employing arylphosphine complexes of palladium and certain inert solvents. More recent methods for the production of such polymers, now known as polyketones or polyketone polymers, are illustrated by a number of published European Patent Applications including 121,965, 181,014 and 213,671. These processes broadly involve the use of a catalyst composition formed from a compound of palladium, cobalt or nickel, the anion of a strong nonhydrohalogenic acid and a bidentate ligand of phosphorus.
The polyketone polymers are produced in the gas phase, e.g., U.S. Pat. No. 4,778,876, or in a liquid phase in the presence of a liquid diluent. Many if not most polymerizations are conducted in a liquid phase and reactant contact during the polymerization is facilitated by application of some type of agitation of the reaction mixture, frequently stirring.
During a polymerization of this type on a large and possibly commercial scale, a number of factors are important to achieve efficient polymerization. Reaction or polymerization rate, i.e., the rate at which the polymer is produced per unit quantity of catalyst, or of the palladium therein, is obviously important. In general, the faster the reaction rate the larger the quantity of polymer that is produced in unit time. Also important, however, is the bulk density of the polymer product. As a rough approximation, the maximum polymer suspension concentration, i.e., the maximum concentration of polymer product suspended in the reaction medium as polymerization takes place, as expressed in kilograms of polymer per cubic meter (kg/m.sup.3) suspension volume, is about one-tenth the bulk density of the polymer product, expressed in kg/m.sup.3. For example, producing a polymer having a bulk density of 10 kg/m.sup.3 will normally permit a suspension concentration of 100 kg/m.sup.3. If the bulk density were increased to 50 kg/m.sup.3, a suspension concentration of about 500 kg/m.sup.3 could be obtained. Expressed differently, the greater the bulk density of the polymer product, the more polymer is produced in a given reaction volume. Moreover, the recovery and washing of a polymer product is greatly simplified when polymer of high bulk density is produced. For example, a polymer of 100 kg/m.sup.3 binds about 5 g of diluent or washing liquid per kg of product, whereas that quantity of liquid is only about 0.25 kg of liquid for a polymer having a bulk density of 500 kg/m.sup.3. It is also known that the higher the bulk density of a polymer the more likely it can be used as such without additional processing. It would be of advantage to provide a process for the production of linear alternating polymers of higher bulk density.